Investigation of bromide ion effects on disinfection by-products formation and speciation in an Istanbul water supply

Recent epidemiological studies reported that brominated DBPs may be more carcinogenic than their chlorinated analogs. Thus, this research was designed to investigate the role of bromide ion in the formation and speciation of disinfection by-products (DBPs) during chlorination of Buyukcekmece Lake Water (BLW) in Istanbul. Chlorination of BLW samples was carried out at pH 7.0 with 5 and 12 mg/l chlorine dosages. For each chlorine dosage, six bromide concentrations ranging from 0.05 to 4.0mg/l were added to form a 2 x 6 experimental matrix. In general, increasing bromide concentration gradually shifted trihalomethanes (THMs) and haloacetic acids (HAAs) speciation from chlorinated species to the mixed bromochloro species during chlorination. The halogen substitution ability of HOBr and HOCl during the formation of THMs and HAAs can be estimated through the use of probability theory. It was concluded that, in both halogen substitution for THM and dihalogenated HAA formation, HOBr was found to be 20 times more reactive than HOCl.     

Occurrence of disinfection by-products in low DOC surface waters in Turkey

A total of 29 surface waters from different regions of Turkey were sampled once a month during 2004. Filtered raw water samples were characterized, chlorinated and the concentrations of disinfection by-products (DBPs) were measured. All waters were low in DOC ranging from 0.91 to 4.42 mg/L. The range of annual average trihalomethanes (THMs) and haloacetic acids (HAAs) concentrations in all waters was 21-189 and 18-149mug/L, respectively. Total mass contributions of halides in THMs and HAAs to absorbable organic halides (AOX) ranged between 10 and 56% in all waters on annual average basis, indicating that significant amounts of other DBPs are being formed in the majority of the tested waters. A strong linear correlation was obtained between the concentrations of THMs and HAAs. Rather poor correlations were found for THMs-AOX and HAAs-AOX levels. For both THMs and HAAs, chlorinated species dominated over brominated ones since the majority of water sources had very low bromide levels. While chloroform and trichloroacetic acid were the major THM and HAA compounds, respectively; the extent of formation and speciation of DBPs varied greatly by season and water source. No consistent general trends were observed in terms of seasonal variations in DBP levels, suggesting that the characteristics of NOM moieties and their chlorine reactivity vary by season in almost all waters tested.     

Screening and estimating of toxicity formation with photobacterium bioassay during chlorine disinfection of wastewater

Reclamation and reuse of wastewater is one of the most effective ways to alleviate water shortage. Disinfection plays a key role in killing the harmful pathogens in reclaimed water, while an unwanted side effect is the formation of disinfection by-products (DBPs). Recently, a number of researches have been conducted on the formation regularities of certain DBPs. However, with current physiochemical techniques, it is impossible to detect all the DBPs. In this study, photobacterium bioassay was used to measure the formation of DBPs and their toxic effect as a whole. The effects of water quality characteristics and operational conditions on the toxicity formation during wastewater chlorination disinfection process were evaluated. A statistical model, depending on chlorine disinfectant dosage, concentration of ammonia nitrogen, and concentration of dissolved organic carbon, was developed to quantitatively estimate the toxicity formation during the disinfection process. It was found that the toxicity of the wastewater samples was positively correlated with chlorine disinfectant dosage, concentration of dissolved organic carbon and UV absorbance at 254nm, while negatively correlated with concentration of ammonia nitrogen.     

Formation of disinfection by-products in the chlorination of ammonia-containing effluents: significance of Cl2/N ratios and the DOM fractions

The presence of ammonia nitrogen (NH(3)-N) in the effluent strongly affected the formation of disinfection by-products (DBPs) during its chlorination. The effect of chlorine (as mg/L Cl(2)) to NH(3)-N (as mg/L N) mass ratios (Cl(2)/N) and the chemical fractions of dissolved organic matter (DOM) in the effluent on the DBPs formation was investigated. Results indicated that the formation of DBPs increased with increasing Cl(2)/N. The concentration and speciation of DBPs varied among different DOM fractions at different zones of chlorination breakpoint curves. The formation rate of total haloacetic acids (THAA) and total trihalomethanes (TTHM) was promoted after the chlorination breakpoint, whereas the reaction of monochloramine with HOCl to dichloramine may cause a decrease in the DBPs formation potential thereafter. Organic acids were found to be the dominant precursors of DBPs with or without the presence of NH(3)-N, which indicated that the CC, CO and C-O structures contributed to the formation of DBPs significantly. In addition, the incorporation of bromine in THMs of the HiA fraction increased with the increasing of Cl(2)/N mass ratios before the chlorination breakpoint, but decreased sharply after the breakpoint. ΔA(280) (absorbance at 280 nm), defined as A(280,initial)-A(280,final), was proved to be linearly related to the TTHM and THAA of wastewater without containing Br(-) during chlorination or chloramination.     

Quantitative detection of trichloroacetic acid in human urine using isotope dilution high-performance liquid chromatography-electrospray ionization tandem mass spectrometry

The chemical disinfection of drinking water to control microbial contaminants results in the formation of disinfection byproducts (DBPs). The volatile trihalomethanes and the nonvolatile haloacetic acids (HAAs) are the most prevalent DBPs. It is important to monitor human exposure to HAAs because of their potential adversehealth effects, such as cancer. Among the HAAs, urinary trichloroacetic acid (TCAA) is a potential valid biomarker for assessing chronic ingestion exposure to HAAs from drinking water. We have developed a rugged, high-throughput, sensitive, accurate, and precise assay for the measurement of trace levels of TCAA in human urine using a simple solid-phase extraction (SPE) cleanup followed by isotope dilution high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). TCAA is extracted from the urine using SPE, separated from other extract components by reversed-phase HPLC, and analyzed by negative ion electrospray ionization-isotope dilution-MS/MS using a multiple reaction monitoring experiment. The method is simple and fast and is not labor intensive (sample preparation and analysis can be performed in approximately 15 min) with a limit of detection of 0.5 ng/mL in 1 mL of urine.     

A GIS-based evaluation of risks due to trihalomethane exposure during showering in coastal Texas

Disinfection of water supplies with chlorine is essential to water treatment, but can lead to the formation of trihalomethanes (THMs) in the presence of natural organic matter. Exposure to THMs via inhalation during daily activities such as showering can significantly increase cancer risks. An innovative decision support system was developed for evaluating THM exposure and risks in water supplies in the Gulf Coast region of Texas by combining a shower THM volatilization model, geospatial analysis techniques, and risk assessment methodologies. Based on THM data from fourteen locations in the region, a power-law equation was developed to predict the formation of THMs in groundwater wells. Health risks associated with THMs in the water supplies of the Gulf Coast of Texas were evaluated. Cancer risks were found to vary from 7.14?×?10^?7 to 7.75?×?10^?6. While two-thirds of the geographical area was below the threshold risk of 1?×?10^?6, it accounted for only a tenth of the total population. Metropolitan areas such as Corpus Christi and McAllen, which currently use surface water sources, and Houston, which is seeking alternate water sources due to subsidence issues, were found to have significant cancer risks (in excess of one in a million). A third of the population of Texas is housed in the Gulf Coast region, and with more population migration toward the metropolitan areas, it is recommended that water resource management decisions be made taking into consideration both the quantity and quality of water available.     

Removal of trihalomethanes from drinking water by nanofiltration membranes

Chlorine reacts with the natural organic matter (NOM) in waters and forms disinfection by-products (DBP). Major of these by-products are trihalomethanes (THM) and haloacetic acids (HAA). They have been known to cause cancer and other toxic effects to human beings. This study determined the removal efficiencies of THM by nanofiltration (NF) techniques with NF200 and DS5 membrane. The rejection of this chlorination by-products was studied at various feed concentration by changing transmembrane pressure. Experimental results indicated that in general increasing operating pressure produces a higher flux but does not have a significant effect on THM rejection. On the other hand, increasing the feed concentration produces a little change in the overall flux and rejection capacity. NF200 membrane removed more THM than DS5 membrane. The higher removal efficiency of dibromochloromethane (DBCM) was attributed to brominating characteristics (higher molecular weight (MW) and molecular size). As a consequence, the results of this study suggest that the NF membrane process is one of the best available technologies for removing THM compounds.     

Disinfection byproducts in Canadian provinces: associated cancer risks and medical expenses

Chlorination for drinking water forms various disinfection byproducts (DBPs). Some DBPs are probably linked to human cancer (e.g., bladder, colorectal cancers) and other chronic and sub-chronic effects. This emphasizes the need to understand and characterize DBPs in drinking water and possible risks to human health. In this study, occurrences of DBPs throughout Canada were investigated. Trihalomethanes (THMs) were observed to be highest in Manitoba followed by Nova Scotia and Saskatchewan, while haloacetic acids were highest in Nova Scotia followed by Newfoundland and Labrador. Based on the characterization of DBPs, risk of cancer from exposure to THMs was predicted using ingestion, inhalation and dermal contact pathways of exposure. In Canada, approximately 700 cancer cases may be caused by exposure to THMs in drinking water. Medical expenses associated with these cancer incidents are estimated at some $140 million/year. Expense may be highest in Ontario (～$47 million/year) followed by Quebec (～$25 million/year) due to a greater population base. This paper suggests improvements in water treatment, source protection and disinfection processes, and caution in the use of alternative disinfectants to reduce DBPs. Finally, elements are provided to mitigate risks and reduce cost estimates in future studies.     

Cu(II)-catalyzed THM formation during water chlorination and monochloramination: A comparison study

The catalytic effect of Cu(II) on trihalomethane (THM) formation during chlorination and monochloramination of humic acid (HA) containing water was comparatively investigated under various pH conditions. Results indicate that in the presence of Cu(II), the formation of THMs was significantly promoted as pH decreased in both chlorination and monochloramination. More THMs were formed during Cu(II)-catalyzed monochloramination which was partially due to enhanced hydroxyl radical (OH) generation as demonstrated by electron spin resonance (ESR) analysis. To discriminate the reactive moieties of HA, nine model compounds, which approximately represented the chemical structure of HA, were individually oxidized by chlorine or monochloramine. Results show that Cu(II) could promote THM formation through reacting with citric acid and similar structures in HA. During chlorination and monochloramination of citric acid in the absence of Cu(II), major intermediates including chlorocarboxylic acid, chloroacetone and chloroacetic anhydride were identified. However, the catalysis of Cu(II) did not produce any new intermediate. The complexation of Cu(II) with model compounds was characterized via FTIR analysis. The reaction mechanism for Cu(II)-catalyzed THM formation was proposed to comprise two pathways: (1) indirect catalysis in which OH oxidizes the large molecules of HA into small ones to enhance THM formation; and (2) direct catalysis in which Cu(II) complexes with HA to accelerate the decarboxylation steps for THM formation.     

Assessing the effect of initial vapor-phase concentrations on inhalation risks of disinfection-by-products (DBP) in multi-use shower facilities

Inhalation during showering activities is a major pathway for exposure to volatile disinfection-by-products (DBPs). Disinfection-by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs) have been shown to significantly increase cancer risks and can also pose other health hazards. In multi-family residences and common-shower facilities located in dormitories and gymnasiums, the time-lag between showers is likely to be short and the exposure to vapor-phase DBPs may be significantly increased due to residual concentrations from earlier showering activities. Current models do not consider the impacts of the initial vapor-phase concentration on health risks to be significant. The hypothesis that non-zero initial DBP vapor-phase concentrations lead to higher exposure and health risks was evaluated here using data from the City of Corpus Christi, TX at two levels of input parameter uncertainty. The inhalation risks and hazards were found to be over 1.5 times greater for subsequent showers compared to the initial shower of the day. For non-zero initial air concentrations and triangular distribution of input parameters, the model was found to be most sensitive to the initial air concentrations, highlighting the impact of initial conditions on cumulative daily intake (CDI) and subsequently on cancer risks and hazard indices. Increasing the time-gap between showers and improving ventilation are viable solutions to contend with the increased risk. It is recommended that the effects of initial air concentrations be incorporated in future risk assessments focusing on multi-family residences in older and poor neighborhoods where single shower dwellings are more common.     

The variation of mass and disinfection by-product formation potential of dissolved organic matter fractions along a conventional surface water treatment plant

Dissolved organic matter (DOM) influences many aspects of water treatment, including the formation of potentially harmful disinfection by-products (DBPs) when disinfectants are applied. DOM from a conventional surface water treatment plant (WTP) in Northern New Jersey was isolated and fractionated using resin adsorption chromatography into six different fractions. These fractions are operationally categorized as hydrophobic acid, hydrophobic neutral, hydrophobic base, hydrophilic acid, hydrophilic neutral and hydrophilic base. The hydrophilic acid fraction was found to be the most abundant fraction in the source water. The hydrophilic neutral, hydrophilic acid and hydrophobic acid fractions had the highest removal efficiency through the WTP (about 65%). The variation and removal effectiveness of each fraction along the WTP was studied. Seven-day chlorine DBP formation potential (FP) tests were performed on all DOM fractions through the WTP. For the source water studied, the hydrophilic acid fraction was found to be the most reactive precursor to the trihalomethane (THM) formation. The hydrophobic neutral fraction was found to be the fraction of concern with respect to the FP of haloacetic acids (HAAs) class of DBPs. The FP of each fraction's class of DBPs was found to be amenable for reduction along the treatment train, specifically by coagulation/sedimentation. The fractionated approach concept showed to be very beneficial in the study of DBP precursors and their effective removal by physical and chemical treatment.     

Characterization of precursors to trihalomethanes formation in Bangkok source water

Resin adsorption techniques using three types of resin (DAX-8, AG-MP-50, and WA-10) were employed to characterize the raw water (RW) from the major 3 million m³/day (793 million gal/day) drinking water treatment plant in Bangkok, Thailand. The dissolved organic carbon (DOC) mass distribution sequences of the six organic fractions in raw water, from high to low, were hydrophilic neutral (HPIN), hydrophobic acid (HPOA), hydrophilic acid (HPIA), hydrophobic neutral (HPON), hydrophilic base (HPIB), and hydrophobic base (HPOB). HPIN and HPOA were the two main precursors for trihalomethanes formation (THMFP) in this water source following chlorination. The chlorination of HPON and HPIN fractions only led to the formation of mostly chloroform, while other organic fractions formed both chloroform and bromodichloromethane. The linear dependency between each organic fraction concentration and THMFP indicated that the reactions of each organic fraction with chlorine were first-order.     

Trihalomethanes formation potential of shrimp farm effluents

Shrimp farm effluents along the Bangpakong River in the Chachoengsao Province of Thailand were evaluated for their trihalomethane formation potential (THMFP) and related parameters. The dissolved organic carbon (DOC), salinity and bromide ion concentrations of shrimp farm effluents were in the ranges of 12-14 mg/L, 0.1-14.5 ppt, and 0-14 mg/L, respectively. The dissolved organic matter was fractionated into hydrophobic and hydrophilic fractions having a range concentration of 3-5 and 8-10mg/L, respectively. The THMFP for all shrimp farm effluents analyzed was in the range of 810-3100 microg/L. The hydrophilic organic fraction was found to be a more active precursor of trihalomethanes (THMs) with 700-966 microg/L THMFP obtained from this fraction, while only 111-363 microg/L THMFP was derived from the hydrophobic fraction. The experimental results showed that salinity and bromide played crucial roles in the formation of THMs. At low salinity and bromide levels, chloroform was the dominant THM species, whereas at high salinity and bromide levels, bromoform became the dominant species. A Fourier Transform Infrared (FTIR) spectrum analysis of the samples before and after chlorination illustrated that the functional groups involved in the THM formation reaction were phenolic compounds, amines, aromatic hydrocarbons, aliphatic bromo-compounds, and aliphatic chloro-compounds.     

Chlorination of organophosphorus pesticides in natural waters

Unknown second-order rate constants for the reactions of three organophosphorus pesticides (chlorpyrifos, chlorfenvinfos and diazinon) with chlorine were determined in the present study, and the influence of pH and temperature was established. It was found that an increase in the pH provides a negative effect on the pesticides degradation rates. Apparent second-order rate constants at 20 degrees C and pH 7 were determined to be 110.9, 0.004 and 191.6 M(-1) s(-1) for chlorpyrifos, chlorfenvinfos and diazinon, respectively. A higher reactivity of chlorine with the phosphorothioate group (chlorpyrifos and diazinon) than with the phosphate moiety (chlorfenvinfos) could explain these results. Intrinsic rate constant for the elementary reactions of chlorine species with chlorpyrifos and diazinon were also calculated, leading to the conclusion that the reaction between hypochlorous acid and the pesticide is predominant at neutral pH. The elimination of these pesticides in surface waters was also investigated. A chlorine dose of 2.5 mg L(-1) was enough to oxidize chlorpyrifos and diazinon almost completely, with a formation of trihalomethanes below the EU standard for drinking water. However, the removal of chlorfenvinfos was not appreciable. Therefore, chlorination is a feasible option for the removal of organophosphorus pesticides with phosphorothioate group during oxidation and disinfection processes, but not for the elimination of pesticides with phosphate moiety.     

Relationship of chlorine decay and THMs formation to NOM size

Because of increasing concern about balancing health risks for pathogen control and disinfection by-product (DBP) formation in water supplies, utilities are forced to closely examine and optimize their disinfection practices. A better understanding of the relationship between the molecular weights of the natural organic matter (NOM), chlorine decay kinetics and THMs formation can help the utilities to minimize the DBP concentrations, providing healthier and microbially safer water. The authors present data on chlorine decay kinetics and total trihalomethanes (TTHM) formation kinetics and modeling with different molecular weights NOM fractions of Mississippi River water. TTHM modeling results indicated that the TTHM formation in fractionated NOM was a function of chlorine consumption. TTHM yield coefficients ranged from 31 to 42 microg-TTHM/mg-Cl2. As the molecular weight of the fractions decreased, TTHM yield coefficients increased.     

Ecotoxicological screening of reclaimed disinfected wastewater by Vibrio fischeri bioassay after a chlorination–dechlorination process

It is well known that different substances can react with chlorine in a water disinfection process to produce disinfection by-products (DBPs). Some of these substances have proven to be carcinogenic in humans and animals. Because it is not possible to detect all DBPs produced in chlorinated wastewater, toxicity tests have been proposed as a useful tool for screening toxic chemicals in treated wastewater. In this study, the Microtox^® bioassay with Vibrio fischeri was used to evaluate the formation of toxic by-products in wastewater, after a chlorination–dechlorination disinfection treatment. All the variables were found to be normally distributed, so analysis of variance could be directly applied without transformation of variables. Significant correlations were obtained between toxicity values and total carbon, total inorganic carbon, total nitrogen, chlorine, and pH. In contrast, total organic carbon, chemical oxygen demand, electrical conductivity and turbidity had no effect on toxicity formation. Toxicity increased with the Cl₂:NH₄⁺ ratio at a higher chlorine concentration released from combined chlorine. Regression models provided a good fit for effective concentration (EC50) as a function of total carbon and total nitrogen, after 5, 10, and 15 min of exposure. These models had greater multiple determination coefficients than previously reported for similar studies, without autocorrelation in the residuals as indicated by the Durbin–Watson statistic test. The measured and predicted ecotoxicity values were strongly correlated.     

Effect of bromide ion on isolated fractions of dissolved organic matter in secondary effluent during chlorination

The role of bromide ion in the trihalomethane (THM) formation and structure of dissolved organic matter (DOM) during chlorination of the secondary effluent taken from the Wenchang Wastewater Treatment Plant (Harbin, China) was investigated. DOM was fractionated using XAD resins into five fractions: hydrophobic acid (HPO-A), hydrophobic neutral (HPO-N), transphilic acid (TPI-A), transphilic neutral (TPI-N) and hydrophilic fraction (HPI). The patterns of individual THM species with increased bromide concentrations were similar for all DOM fractions. The THM speciation as well as halogen fraction for these five fractions followed similar trends with the Br(-)/Cl(2) ratio. Chlorination resulted in decreased ultraviolet (UV) absorbance across wavelengths from 250 to 280 nm for DOM fractions whether bromide ions existed or not, and bromide addition led to lower differential UV absorbance values. Fourier-transform infrared (FT-IR) results indicated that chlorination, whether bromide ions existed or not, resulted in the near elimination of aromatic CH and amide peaks, increased CO absorption intensity and occurrence of CO and CCl peaks for HPO-A, HPO-N, TPI-A and TPI-N. Furthermore, bromide addition in chlorination led to the occurrence of CBr peak for all four fractions.     

Genotoxic evaluation of the non-halogenated disinfection by-products nitrosodimethylamine and nitrosodiethylamine

Disinfection by-products (DBPs) are chemicals that are produced as a result of chlorine being added to water for disinfection. As well as the halogenated DBPs, N-nitrosamines have recently been identified as DBPs, especially when amines and ammonia ions are present in raw water. In this work, the genotoxicity of two nitrosamines, namely nitrosodimethylamine (NDMA) and nitrosodiethylamine (NDEA), has been studied in cultured human cells. To evaluate their genotoxic potential two assays were used, the comet assay and the micronucleus test. The comet assay measures the induction of single and double-strand breaks, and also reveals the induced oxidative DNA damage by using endoIII and FPG enzymes. Chromosomal damage was evaluated by means of the cytokinesis-blocked micronucleus test. The results of the comet assay show that both compounds are slightly genotoxic but only at high concentrations, NDEA being more effective than NDMA. Enzyme treatments revealed that only NDEA was able to produce increased levels of oxidized bases, mainly in purine sites. The results obtained in the micronucleus assay, which measures the capacity of the tested agents to induce clastogenic and/or aneugenic effects, are negative for both of the nitrosamines evaluated, either using TK6 cells or human peripheral blood lymphocytes. Taking into account the very high concentrations needed to produce DNA damage, our data suggest a low, if existent, genotoxic risk associated with the presence of these compounds in drinking water.     

高锰酸钾与氯联用消毒控制饮用水中三卤甲烷生成量

主要考察了高锰酸钾与氯联用消毒工艺的化学安全性。研究了氯投量、高锰酸钾投量、Br^-浓度和pH值等因素对高锰酸钾与氯联用消毒工艺三卤甲烷(THMs)生成量及生成形态的影响。结果表明：氯投量对THMs生成量及生成形态有显著影响。随着氯投量的增大,THMs生成量显著升高,且溴代三卤甲烷(Br-THMs)占主要部分。高锰酸钾投量对THMs生成影响较小。THMs与Br-THMs的生成量随着Br^-浓度及pH值的升高而增加。与单独氯消毒工艺比较,高锰酸钾与氯联用消毒减少了氯投量,降低了THMs的生成量。高锰酸钾与氯联用消毒工艺在保障饮用水的化学安全性上优于单独氯消毒工艺。     

Characterization of isolated fractions of dissolved organic matter from sewage treatment plant and the related disinfection by-products formation potential

Dissolved organic matter (DOM) in effluent from a conventional sewage treatment plant was isolated using resin adsorbents into six classes: hydrophobic bases (HoB), hydrophobic acids (HoA) and hydrophobic neutrals (HoN); hydrophilic bases (HiB), hydrophilic acids (HiA) and hydrophilic neutrals (HiN). Organic acids were the most abundant fractions of DOM. Hydrophobic organics especially hydrophobic acids were found to have higher overall disinfection by-products formation potential (DBPFP). Moreover, the potential decreased as the sequence of acids, neutrals and bases. Ultraviolet spectrophotometry at 254nm (UV(254)), fluorescence spectroscopy, size exclusion chromatography and Fourier transform infrared spectroscopy (FTIR) were employed to characterize DOM fractions. And the relationship between the characteristics of DOM fractions and the related DBPFP was discussed in detail. It was found that UV(254) to DOC ratio (SUVA) exhibited a positive correlation with haloacetic acids (HAAs) formation potential whereas distinctive linear correlation was not observed between SUVA and trihalomethanes (THMs) formation potential. Of the fluorescence organics contained in DOM, humic acids exhibited higher chlorine reactivity than fulvic acids. Smaller molecules of humic acids produced more DBPs. Furthermore, a combination of aromatic moieties and aliphatic structures with nu(C_O) groups contributed largely to the formation of DBPs.